A fuming furnace is a common non-ferrous smelting device which is used for treating slag when smelting lead and zinc. When the fuming furnace of the related art is used for treating leaded materials, the lead will be deposited at the bottom of a molten pool in the furnace if the lead content is too high. The deposited lead causes damage to the furnace (furnace bottom water jacket and furnace wall water jacket), which leads to a water seepage or even an explosion in severe cases, thereby there existing requirements for improvements. At the same time, the improvements will also enhance the treating ability and adaptability of the fuming furnace to the leaded materials with high lead content.